Age Response for Line CHO Chinese Hamster Cells Exposed to X-Irradiation and Alpha Particles from Plutonium

The age response of Chinese hamster cells (line CHO) synchronized by mitotic selection and by mitotic selection with hydroxyurea resynchronization was studied for x rays and alpha particles from plutonium of 4.4-MeV residual energy. The age response for alpha particles when mitotically synchronized cells are used indicated that cells in S are slightly more sensitive but that the magnitude of variation is quite small. When cells were synchronized first by mitotic selection and then resynchronized by hydroxyurea, the variation of radiosensitivity as a function of cell cycle for x rays was found to be enhanced because of a higher degree of synchrony. In the case of alpha particles, it was found that cells in late S were more sensitive and that there was a clear peak of resistance corresponding to cells in G$sub 2$/early G$sub 1$. (auth)